1. Technical Field
The present invention relates to a field in which telop characters in a video image are extracted in order to utilize them for a video retrieval text or the like. More particularly, it relates to a field in which a binary character pattern for use in character recognition is extracted from a telop region in a video image.
2. Description of the Related Art
In recent years, a DVD apparatus and an HDD video apparatus each of which can record a large number of programs have come into wide use in order to view a multiplicity of channels. As a result, there have risen needs for retrieving favorite contents from among the large quantity of recorded videos.
For such retrieval from among the large quantity of videos, it is required to automatically extract and textize telop characters in a video image.
As a related-art method for extracting and textizing the telop character, it is assumed that the telop character has the highest luminance in a frame image, and only the pixels of a peak part at which a luminance distribution is the highest are extracted from within a telop region and are outputted as constituting a telop character pattern (refer to JP-A-2000-182053).
In another method, candidate patterns are created by various techniques, the respective candidate patterns are subjected to character recognitions, and a specified one of the candidate patterns is selected as telop information in accordance with recognition reliabilities exhibited till the character is recognized (JP-A-2001-285716). In this method, as a process in which pixels constituting a telop character are extracted from the background, the luminance histogram of an edge inflation region is obtained. Luminance peaks are obtained for a telop and the edge and background of the telop, and a distribution of the highest peak is identified as the distribution of the telop character, thereby to extract the candidate pattern.
However, the telop character extraction of JP-A-2000-182053 extracts the pixels assuming that the telop character has the highest luminance in the frame image. Therefore, it has the problem that a telop character of low luminance cannot be recognized.
The extraction of the telop character according to JP-A-2001-285716 selects the telop information from among the character recognition results of the plurality of candidate patterns obtained for a telop region, in accordance with the recognition reliabilities. It does not extract one telop character pattern from within a frame image for the purpose of character recognition, and processing becomes complicated.
Besides, the method of JP-A-2001-285716 extracts the distribution of the highest peak in the luminance histogram of the edge inflation region, as the distribution of the telop character in order to extract the pixels constituting the telop character from the background. This results in the problem that a telop character of low luminance cannot be recognized.
Therefore, the present invention has for its object to provide telop character extraction in which a telop character pattern is extracted at a high precision without depending upon the luminance of a telop character, and even telop characters of low luminance and medium luminance are extracted, whereby a recognition rate can be enhanced.